Control for constant-speed, variable-pitch propellers



Feb. 17, 1953 B. H. SLATTER ET AL CONTROL FOR CONSTANT-SPEED, VARIABLE-PITCH PROPELLERS Filed Oct. 1, 1947 Zla 23 5 Sheets-Sheet 1 Feb. 17, 1953 B. H. SLATTER ETAL 2,623,684

CONTROL. FOR CONSTANT-SPEED, VARIABLE-PITCH PROPELLERS Filed Oct. 1, 1947 5 Sheets-Sheet 2 M/I/E/VTORS 55 H. SMITH? at Feb. 17, 1953 a. H. sLATTER ET AL CONTROL FOR CONSTANT-SPEED, VARIABLE-PITCH PROPELLERS 5 Sheets-Sheet 3 Filed Oct. 1, 1947 A s .N T s "L J I A 1 l/WE/l/TUF B H. 51197727 I a. mls/l 57% 1 W HTT'IS.

Feb. 17, 1953 H. SLATTER ETAL CONTROL FOR CONSTANT-SPEED. VARIABLE-PITCH PROPELLERS 5 Sheets-Sheet 4 Filed Oct. 1, 1947 I/Wf/WMS I 5". H. 55/2775 7." G Dfl/SH 57% X Q/ZZWA Feb. 17, 1953 a. H. SULATTER ETAL CONTROL FOR CONSTANT-SPEED, VARIABLE-PITCH PROPELLER'S 5 Sheets-She 5 Filed Oct. 1, 1947 I w mm w 540 n IL W3 n He m Patented Feb. 17, 1953 CONTROL FOR CONSTANT-SPEED, VARIABLE-PITCH PROPELLERS Brian H. Slatter and Thomas G. Daish, Coventry, England, assignors to Armstrong Siddeley Motors Limited, Coventry, England Application October 1, 1947, Serial No. 777,262 In Great Britain J nne 21, 1947 In instances where a constant-speed, variablepitch propeller of an aircraft, is to be driven by an internal-combustion turbine unit, the movement of the control element of the constantspeed mechanism (to vary the datum setting of the constant-speed mechanism) may be directly effected by movement of the pilots throttle control which also adjusts the fuel supply.' This arrangement, however, has the disadvantage that when the throttle control is moved to increase the fuel supply the unit speeds up, under low load, to above the selected speed before the constant-speed mechanism (which is responsive to the speed of the unit) can correspondingly coarsen the pitch of the air-screw for developing the requisite power, with the result that relatively violent fluctuations occur in the speed and power of the unit before the latter settles down to operate at the selected speed.

By increasing the datum setting of the constant-speed mechanism we mean adjusting it so that the unit will run faster, and by decreasing the said setting the reverse is meant.

Our main object is to provide means whereby the unit can be rapidly accelerated to the se-- lected speed and power with a minimum of hunting (i. e., variations above and below the selected speed). 7

According to the invention, a constant-speed, variable-pitch propeller, which is to be driven by an internal-combustion turbine unit, has the movable control element of the constant-speed mechanism connected to the throttle control of the unit through a hydraulic time-delay device such that, when the throttle control is moved to increase the fuel supply to the unit, the datum setting of the constant-speed mechanism is initially increased at a relatively-low rate, then at a relatively-high rate, and finally at a relatively-low rate, so as to enable the unit rapidly to assume the selected speed and power without undesirable fluctuations.

In the accompanying drawings:

Figure 1 is a diagram illustrating a hydraulic time-delay device for effecting the control according to the invention, three coaxial portions of the valve means being shown one below the other for convenience and marked A, B and C for facilitating the showing of their respec-c 5 Claims. (01.170-135374) Figure 3 is a view, on the line 3-3 of Figure- 4, of the control showing linkage actuatedshown separated but with their coacting ports and lands aligned in the same radial planes they occupy when in assembled position, and

Figure 7 shows developments into the flat of the ported sleeve and rotary valve member in the same relative positions as shown in Figure 6.

In the drawings, and particularly in Figure l the hydraulic servomotor shown includes'a. into two compartments Ila, Hb bya vane l2 which is' working chamber which is divided fast with a sleeve having two coaxial portions i3, 32' and rotatably supported on a rotary valve member having coaxial portions I4, I40: with which the throttle lever (Figure 5) for the turbine unit is connected. (Although, in

Figure 1, the sleeve and valve member are shown in three portions spaced one above another, that has been done purelyforease of illustration, those portions being, in fact, coaxial with one another and integral as show by Figure 4.) v l A supply pipe I6 for hydraulic fluid underpressure is connected by apipe 18 (Figures 1 and 4) through a restrictor valve I! i (Figures 1 and 4) to a pipe I 8a terminating in an-annular passage 62, in the-casing [9 or a liner- 234 therein, from which ports 20a and 20b in the sleeve portion I3 are fed for supplying the pressure fluid to an annular groove I00 in the valve member as shown at C in Figure 1. This groove I 00 communicates with valve chambers 23:: and 24:: (shown at B in Figure 1) defined between two lands 29a, 29b of the valve memberportion Mar, which lands are in. peripheral, contact with the bore of the sleeve portion I31.

These valve chambers are extended axially to form narrower valve chambers 23 and 241 as shown at A in Figure 1. v

The vane I2 is shown in an intermediate position in Figurefl, and, in this position, an initial rotation of the. valve member portion v l4 in the clockwise direction(foraccelerating the the ported sleeve and rotary valve member of Figure 4' turbine unit) causes the land 2la to uncover a port 22a in the sleeve and to admit the pressure fluid to the portion lla of the working chamber, thus driving the vane in the clockwise sense (Figure l). The portion l4 has four of these lands two of which define the valve chamber 23 for coaction with the port 22a for acceleration control, while two define the valve chamber 24 for coaction with the port 22b for deceleration control, the sleeve port 22b being provided for coaction with the land 2lb.

The sleeve portion I31: (indicated at B in Figure 1) has a pair of ports 26a, 26b to which pressure fluid from the pipe It can respectively be delivered through a pipe 21 terminating in an annular passage 54 in the bore of the casin portion I92: (Figure 1) or liner 234 (Figure 4), a restrictor valve 28 being provided as necessary in the supply pipe 21.

The two diametrically-opposite lands 29a, 29b of the valve member portion |4x overlap the respective coacting ports 25a, 261) by a greater amount (say, each side of the central position) than the ports 22a, 22b are overlapped by the lands Zla, 2lb.,

If the valve member is rotated relatively quickly and to a sufficient extent (for example, in a clockwise direction), then, after the aforesaid initial supply of fluid pressure to the chamber lla to start the movement of the vane, the land 29a will have uncovered the port 26a, and a further supply of pressure fluid will then be delivered to the compartment Ila from the supply passage 21 by way of the groove 64, the port 25a, the valve chambers 232:, 23, and the port 220, the resultant higher pressure in the compartment Ila then moving the vane at a greater speed than that at which it was initially moved.

Finally the port 26a catches up with and is closed by the land 29a to cut off the additional supply of motive fluid, and shortly afterwards the port 22a has caught up with and is closed by the land 2 la, whereupon the vane l2 remains inoits new position ntil the valve member I4, I40: is again turned.

During this clockwise movement of the vane the hydraulic fluid in the compartment llb is exhausted through the port 22b into the space 32 and through a radial duct l0l of the portion l4 into a bore 33 thereof which is connected to the return side of the hydraulic circuit.

It will be seen that, on moving the throttlecontrol 60 to open the fuel valve (not shown) by the connection 66 as hereinafter described, the datum setting of the constant-speed mechanism 68, which is of known form, is adjusted in three phases as follows:

Firstly, the control element 61 of the constantspeed mechanism is adjusted relatively slowly to permit the turbine unit to speed to a value above that which corresponds to the datum set ting of the constant-speed mechanism, this being done by the fluid entering the compartment lla through the ports 20a and 22a, the resultant movement of the vane l2 and sleeve I3, I31: initiating the second phase;

Secondly, the control element 61 is adjusted at a much greater speed due to the extra supply of hydraulic fluid through the port 26a, spaces 23:: and 23, and port 22a to the compartment Ila, the annular groove 64 permitting this supply after the port 26a has been moved clockwise out of alignment with the end of the pipe 21 by the movementof the sleeve portion I32: during the first hase; and

Thirdly, the control element 61 i moved to complete the adjustment at the same lower speed as that during the first phase, the land 29a being caught by the port 26a and cutting off the additional fuel supply of the second phase.

The effect is illustrated in Figure 2 in which the curve 35 indicates the rate of throttle lever movement (1. e., the rate of fuel delivery to the turbine unit), the curve 36 the speed of the unit, and the curve 31, 38, 39 the datum set ting of the constant-speed mechanism 58. It will be seen that with a smooth throttle lever movement the increase in the datum setting of the constant-speed mechanism is initially caused to lag (curve-portion 31) so that the speed of the turbine unit can rise above the speed corresponding with the datum setting, the constant-speed mechanism then applie the load (as shown at 38), in step with the throttle lever movement, thus reducing the tendency of the unit to over-speed and, finally the remainder of the load is applied at a lower rate (curveportion 39) so as to smooth out any tendency for the unit greatly to exceed, or fall below, the selected speed, which latter is indicated by the curve 40.

In Figures 3 to 5 the throttle control lever 60 is connected, by a link ill, to the arm 42 which is keyed at 43 to the valve member l4, and the sleeve I3 is keyed at 200 to a member 45 havin a cam slot 46 in which is engaged a roller 41 on a lever 10 mechanically connected to the control element 61 of the constant-speed mechanism for controlling the datum setting of the constant-speed mechanism. For effecting this connection the arm 10 is made fast with a shaft 20l which has a bearing in a wall 202 of the casing l9 and extends outwardly thereof. At its outer end the shaft 20l has fast with it a second arm 203 which is connected by a link 204 to one arm 205 of a bell-crank lever pivoted at 206 to a stationary member (not shown). The other arm 20! of the bell-crank lever is connected by a link 208 to one arm 209 of a second bell-crank lever pivoted at 2 H) to a stationary member (not shown) and the second arm 2 of this lever is connected by a link 2l2 to rock, about a pivot 2l3, a toothed quadrant 2- of the constant-speed mechanism.

Keyed at 2l5 to the valve member I4 is an arm 2l6 which is linked at 48 to a second arm 49 which carries a member 50 having a cam slot 5| for similarly adjusting the fuel valve by means of a roller 52 on the bell-crank lever ll connected at 65 to the fuel valve, the arm 49 and member 50 being shown in Figure 3 as Journalled on a pivot 53. Actually the bell-crank lever ll comprises an arm lla by which the roller 52 is carried and which is fast with a shaft llb, journalled in the wall 202, also carrying an arm llc to which latter the link 66 is connected.

For reverse movement of the pilots throttle lever (i. e., to reduce the speed and power 0f the unit by reducing the fuel supply and lowering the datum setting of the constant-speed mechanism 68) the action above described is reversed, the hydraulic fluid then entering the compartment I lb, from the passages 241:, 24 and the associated ports 26b and 22b, and exhausting through the port 22a to the space 32.

Figure 5 shows the control element 61 of the constant speed mechanism acting, through a spring 2 l1 and a governor M8, on a valve member 2l3'1orv controlling a hydraulic supply from a pump 229 to the pitch-changing mechanism (indicated at 22!) of the propeller 222 of a gas turbine unit 223. In the position shown the lands 224 and 225 are respectively blocking supply lines 226 and 22'! to opposite sides of a piston 228 of the pitch changing mechanism and thus hydraulically lock the latter. A relief valve 229 in these conditions by-passes the output of the pump 229 to a passage 239 leading to the pump intake. Movement of the valv member 219 downwardly in the figure directs the pump output through the line 22! to one side oil the piston 228, and movement of the latter expresses the fluid on its opposite side through the line 226 and the passage 239 back to the pump intake. A reverse operation from the position shown of the valve member 219 reversely moves the piston 228 and the fluid is expressed through the line 221 and a further return passage 23! to the pump. As indicated, the piston 228, in known manner, has a rack 232 engaging toothed segments 233 fast with the propeller blades for varying the pitch.

What we claim as our invention and desire to secure by Letters Patent of the United States is:

1. In combination, a fluid pressure servomotor having a fixed element and a movable element with a working chamber between them, said movable servo element having a port through which motive fluid can be supplied to said working chamber, valve means which when rotated admits the motive fluid through said port to said working chamber to rotate said movable servo element to a new .position in which said port is again closed by said valve means, said valve means having two portions angularly rotatable in unison, one of said portions having a land to coact with said port upon rotation of said portions normally to close it, a valve chamber adjacent said land from which motive fluid can be supplied through said port :when said valve member is initially rotated, means for restricting the supply of such motive fluid whereby the response of said movable servo element will be a relatively-slow one, and said other portion Olf said valve means having a valve chamber connected with that first-mentioned, said valve chamber of said second portion being adjacent a land which co-operates with a port movable with said movable servo element for supplying motive fluid to said valve chamber and which overlaps said port to a greater extent than the land firstinentioned overlaps its associated port, whereby motive fluid will be delivered from said secondmentioned port to said working chamber only after the initial movement of said valve member to actuate said movable servo element at a greater speed, said second-mentioned port catching up and being screened by said second-mentioned land before said first-mentioned land catches up and screens said first-mentioned port, so that the final delivery of motive fluid to said working chamber will be at a relatively-low rate through said restricting means.

2. The combination of claim 1, with a constant-speed, variable-pitch propeller driven by an internal-combustion turbine unit, including a constant-speed mechanism controlling the pitch, said mechanism having a control element 6 actuated by a cam which is in turn actuated by said movable servo element.

3. The combination of claim 1, with a constant-speed, variable-pitch propeller driven by an internal combustion turbine unit, including a constant-speed mechanism controlling the pitch, said mechanism having a control element actuated by said movable servo element.

4. In combination, a variable pitch propeller having a constant-speed mechanism and an internal combustion turbine unit driving said propeller, a. throttle control for the turbine unit, a movable control element connected to the constant speed mechanism for varying the datum setting thereof, and a hydraulic time delay mechanism connecting said control element to said throttle control and having means actuated by the throttle control and connected to the control element for initially increasing the datum setting at a relatively low rate in response to a quick movement of the throttle control in increasing the supply of fuel to unit, and for sub sequently increasing the datum setting at a relatively high rate and finally increasing the datum setting at a relatively low rate, so as to enable said turbine unit to rapidly assume the selected speed and power without undesirable fluctuations.

5. In combination, a variable pitch propeller having a constant-speed mechanism and an in ternal combustion turbine uni-t driving said propeller, a throttle control for the turbine unit, a movable control element connected to the constant speed mechanism for varying the datum setting thereof, and a hydraulic time delay mechanism connecting said control element to said throttle control and including a first member connected to and actuated by the throttle control and a second member movable relative to the first member and connected to the control element, said members being hydraulically coupled together :for initially increasing the datum setting at a relatively low rate in response to a quick movement of the throttle control in increasing the supply of fuel to unit, and for subsequently increasing the datum setting at a relatively high rate and finally increasing the datum setting at a relatively low rate, so as to enable said turbine unit to rapidly assume the selected speed and .power without undesirable fluctuations.

BRIAN H. SLATTER. THOMAS G. DAISH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,217,364 Halford et a1. Oct. 8, 1940 2,384,353 Stieglitz Sept, 4, 1945 2,396,618 Stieglitz et a1 Mar. 12, 1946 2,429,189 Maddox Oct. 14, 1947 FOREIGN PATENTS Number Country Date 671,248 France Aug. 31, 1929 

